1. Field of the Invention
The present invention relates generally to a chemical mechanical polishing (CMP) apparatus, and more particularly, to a chemical mechanical polishing apparatus containing cleaning fluid conduits for suppressing micro scratches on a wafer.
2. Description of the Related Art
As the integration of semiconductor devices increases and multi-layered interconnections become widely used, the importance of local and global planarization of an interlevel dielectric layer becomes more important. A preferred planarization method is a chemical mechanical polishing (CMP) method, where a surface of a semiconductor wafer is polished using chemical components of a slurry solution supplied between the wafer and a polishing pad.
In general, CMP equipment includes a polishing platen unit, a polishing head unit and a pad conditioning unit. The polishing platen unit includes a polishing platen connected to a drive motor and a polishing pad on the polishing platen. The drive motor rotates the polishing platen and the pad.
The polishing head unit includes a wafer carrier supporting and applying pressure to the semiconductor wafer, a first ring surrounding the wafer carrier to prevent lateral deviation of the semiconductor wafer during polishing, and a second ring surrounding the first ring. The second ring contacts the polishing pad to improve the polishing profile of an edge portion of the semiconductor wafer.
The pad conditioning unit contains a pad conditioner head connected to a motor shaft, which moves the head over the polishing pad. The pad conditioner head supports a disk holder which includes a diamond disk suspended above the polishing pad. The motor shaft lowers the head toward the polishing pad such that the diamond disk contacts the polishing pad to maintain and/or condition the surface of the polishing pad.
In the above CMP apparatus, the semiconductor wafer is attached to the wafer carrier with the surface of the semiconductor wafer to be polished facing the surface of the polishing pad. The polishing pad and the semiconductor wafer are rotated during polishing. A polishing slurry is supplied during the polishing operation. During polishing, pressure is appropriately applied by the polishing head unit on the semiconductor wafer contacting a first region of the polishing pad to polish the surface of the semiconductor wafer. Meanwhile, the pad conditioning unit is positioned over a second region of the polishing pad so that the surface of the polishing pad is appropriately conditioned and/or maintained by the diamond disk.
However, the prior art CMP apparatus suffers from the following problem. During polishing using the above CMP apparatus, the slurry supplied on the polishing pad may splash up and infiltrate into the gaps and/or holes in the polishing head unit and/or in the pad conditioning unit. For example, the slurry may infiltrate into the gaps between the first ring and the second ring, between the first ring and the wafer carrier, between the pad conditioner head and the disk holder and/or into the holes in the second ring. The infiltrated slurry rapidly solidifies into flakes or particles in the gaps and/or holes.
Although the polishing head unit, the polishing pad and the pad conditioning unit are cleaned from the outside after a polishing cycle, the slurry cannot be properly and completely removed from the gaps and/or holes. During the next polishing cycle, the solidified slurry particles drop away from the gaps and holes where they solidified onto the polishing pad. The solidified slurry particles on the polishing pad contact the wafer being polished and cause micro scratches (i.e., undesirable defects) on the surface of the wafer being polished.
The present invention is directed to overcoming or at least reducing the effects of the problem set forth above.
In accordance with one aspect of the present invention, there is provided a chemical mechanical polishing apparatus, comprising a rotatable polishing pad, a wafer carrier facing in a direction of the polishing pad, at least one ring surrounding the wafer carrier and a first cleaning solution supply conduit located adjacent to the at least one ring for supplying a cleaning solution into at least one gap located in a region between the at least one ring and wafer carrier.
In accordance with another aspect of the present invention, there is provided a chemical mechanical polishing apparatus, comprising a rotatable polishing pad, a wafer carrier facing in a direction of the polishing pad and a pad conditioning unit, containing a pad conditioner head, a drive shaft connected to the pad conditioner head, a disk holder located below the pad conditioner head, such that a third gap is located between the disk holder and the pad conditioner head, a conditioning disk located below the disk holder and a second cleaning solution supply conduit for supplying a cleaning solution to the third gap.
In accordance with another aspect of the present invention, there is provided a method of polishing a substrate, comprising placing the substrate onto a carrier containing at least one ring, lowering the carrier to place the substrate in contact with a polishing pad, supplying a slurry to the polishing pad, rotating the polishing pad to remove a portion of the substrate and supplying a cleaning solution into at least one of (a) at least one gap located in a region between the at least one ring and the carrier to remove the slurry from the at least one gap and (b) a third gap located between a disk holder and a pad conditioner head of a pad conditioning unit to remove the slurry from the third gap.